Congenital heart disease Flashcards
What is a congenital heart defect?
It is a general term used to describe abnormalities of the heart or great vessels present from birth
- Faulty embryogenesis (week 3-8)
- Usually monomorphic (single lesion) like ASD, VSD,
- Might not be evident until adult life (like coarctation or ASD)
- its incidence in the USA is 1%
- Noninvasive methods like Ultrasound, MRI, and CT increases the early detection
Describe the pathogenesis of congenital heart defects
- Faulty embryogenesis during the gestational weeks of 3-8, when the major CVS structures develop
- Unknown in 90% of the cases
- In 10% well defined genetic or environmental influences are identifiable
What are the genetic causes of congenital heart disease?
- Trisomies 21 (down syndrome) along with genes 13, 15, 18, and XO
- Mutation of genes that encode for the transcription factors TBX5 & NKX2.5 results in ASD
- VSD is observed in Holt-Oram syndrome, a rare hereditary condition associated with heart, arm, and hand defects
- Mutation 22q11.2 deletion of chromosome 22, an important chromosome in heart development (conotruncus, brachial arch, and face) observed in 15-50% of the disorders
What are the environmental causes of congenital heart defects?
1) Congenital rubella infection
2) Gestational diabetes
3) Exposure to teratogens (Including some therapeutic drugs) responsible for additional cases
What are the clinical features if congenital heart abnormalities?
- A shunt is an abnormal communication between chambers or BV
1) Left to Right chamber shunt
- Cyanosis can occur due to deoxygenated blood shunting (Eisenmenger syndrome)
- If significant pulmonary hypertension is irreversible
- Septic emboli that arises in the peripheral veins can bypass normal filtration action of the lungs, causing brain infarction and abscess
2) Obstructions
- Coarctation of Aorta
- Pulmonary stenosis/atresia
- Aortic stenosis/atresia
What are the most commonly encountered left-to-right shunts?
1) Atrial septal defect
2) Ventricular Septal Defect
3) Patent Ductus Arteriosus
4) AV septal defect
What is atrial septal defect?
- ASD results in an L-R shunt, as the pulmonary resistance is less than the systemic vascular resistance in addition to the fact that the compliance of the right ventricle is greater than the LV
- ASD is mainly not symptomatic before 30 years old
- A murmur is heard due to the excessive flow through the pulmonary valve
- Eventually volume hypertension of the RA & RV develops
What is ventricular septal defect?
- Incomplete closure of the ventricular septum forming a shunt between LV & RV
- It is the most common CHD
- In 90% of the cases the membranous septum is involved
- In the other 10% when the muscular septum is involved, multiple holes (swiss-cheese-septum) are found
What is the clinical presentation of septal defects?
1) The small ones close spontaneously
2) The large ones with a significant L-R flow will develop RV hypertrophy, and pulmonary hypertension leading to an irreversible pulmonary vascular disease in all patients with large unoperated VSD which will lead to cyanosis and death
What is meant by patent ductus arteriosus?
- When the ductus arteriosus remains open after birth
- It does not produce functional difficulties at birth but a harsh machinery murmur
- an obstructive pulmonary vascular disease might lead to Right to Left shunt as hypertension approaches the systemic pressure
What are the malformations that cause right-to-left shunts?
- All have “T” in their names:
1) Tetralogy of fallout
2) Transposition of great arteries
3) Truncus arteriosus
4) Total anomalous pulmonary venous connection
5) Tricuspid atresia
What is meant by the tetralogy of Fallot?
- The most common form of cyanotic CHD
- Results from the anterior superior displacement of the infundibular septum
1) Large VSD
2) Obstruction to the RV flow (subpulmonary stenosis)
3) Aorta overrides the VSD
4) right ventricular hypertrophy
- These four findings are a must
- Even if untreated the patient will most likely to survive to adulthood, in X-ray it has a boot-shaped sign due to the marked right ventricular hypertrophy
What are the clinical presentations of tetralogy of fallout?
- The severity of the obstruction determines the direction of blood flow, which depends on the pulmonary outflow obstruction
1) No cyanosis if the subpulmonary stenosis is mild, L-R-Shunt
2) In more severe subpulmonary stenosis, R-L-SHUNT and cyanosis will occur
3) With increasing severity of stenosis, the pulmonary artery gets progressively smaller and thinner and the wall gets hypoplastic, the aorta will progressively get larger
- The child grows and the heart increases in size while the pulmonary orifice does not, the obstruction will progressively worsen, and thus most infants are cyanotic from birth
- Complete surgical repair is possible if it is not complicated
What is meant by the transposition of the great arteries (TGA)?
- When the aorta arises from the right ventricle and the pulmonary artery emanates from the left ventricle
- A shunt is needed for survival
- RV thickness is greater than the LV
- Deoxygenated blood from the body (right side) is pumped right back out (aorta). Oxygenated blood coming from the lungs (left side) is being pumped right back to the lungs (pulmonary trunk)
In this case, a shunt is essential for survival. The actual management would be to cut and switch the locations of the arteries. - While waiting for surgery, a medicine called prostaglandin may be used to keep the ductus arteriosus open and allow for better mixing of oxygenated and deoxygenated blood
What is meant by truncus arteriosus?
- It is a developmental failure of separation of the embryologic truncus arteriosus into the aortic and pulmonary artery, where a single great artery receives blood from both ventricles
- It is accompanied by an underlying VSD, which gives rise to the systemic, pulmonary, and coronary circulations
What are the examples of obstructive congenital heart disease?
1) Coarctation of aorta
2) Pulmonary stenosis/atresia
3) Aortic stenosis/atresia
What is meant by the coarctation of the aorta?
- The narrowing/constriction of the aorta, the most important form of obstructive congenital heart disease
- Occurs in males twice more, although females with Turner syndrome commonly have aortic coarctation
- In 50% of cases it is accompanied by a bicuspid aortic valve
What are the different types of the coarctation of the aorta?
1) With PDA
- In infants
- Narrowing plus a shunt between the arteries: blood goes from the pulmonary artery to the descending aorta (due to the obstruction, the BF to the descending aorta is minimized so the pressure in the pulmonary trunk becomes higher than the descending aorta hence the R – L movement) – cyanosis in the lower half and usually presents very early, complicated by the tubular narrowing of the aortic segment
2) Without PDA
- In adults
- Ridgelike unfolding of the aorta distal to the ligamentum arteriosum
- The upper limb will have high pressure while the lower limb will have a low pressure
What are the clinical presentations of coarctation of the aorta with a PDA?
- Depends on the severity of the narrowing and the patency of the ductus arteriosus:
1) Many infants can’t survive the neonatal period without a surgical or catheter-based intervention, delivering unsaturated blood through the ductus arteriosus produces cyanosis localized to the lower half of the body
What are the complications of the coarctation of the aorta without PDA?
- Mostly asymptomatic which might go unrecognized until adult life
- HTN in upper extremities with low pulse and low pressure in the lower extremities
- Collateral develops to compensate for the low pressure in the lower ectrimity
- Thrill/systolic murmur
- Due to the LV hypertrophy there might be cardiomegaly
- surgical resection and end-to-end anastomosis or replacement by a prosthetic graft yields excellent results
What are the most frequent congenital cardiac malformations?
1) VSD (4482/1 MILLION)
2) ASD (1043/1 MILLION)
3) Pulmonary stenosis (836/1 million)
What is heart failure?
A pathologic state where there is an impairment of cardiac function, and thus the heart is unable to maintain sufficient output to meet the metabolic requirements
- It is a common endpoint of many heart disease
- Congested heart failure is complicated by diminished CO (forward flow), and accumulation of blood in the venous system (backward flow)
What is the mechanism by which heart failure can occur?
1) Systolic dysfunction (Abnormal pumping)
- Progressive deterioration of the myocardial contractile function, due to ischemic injury, pressure or volume overload, dilated cardiomyopathy
2) Diastolic dysfunction (a problem in heart filling and relaxation)
- Inability of the heart chambers to relax during diastole, due to left ventricular hypertrophy, amyloidosis (accumulation of amyloid “abnormal protein deposition”), constrictive pericarditis
What are the mechanism that the CVS do to compensate for the reduced myocardial contractility, or increased hemodynaic burden?
1) Tachycardia
2) Ventricular dilation (improves contraction due to the myofibril stretching)
3) Salt and water expansion increasing the blood volume
